CHAPTER EIGHTEEN 



ARGUMENTS FOR EVOLUTION 







I. IT is one thing to show how evolution might have Obstacles 

 occurred, and another to demonstrate it as a fact. understand- 

 Modern naturalists are more nearly unanimous about in of . 

 the demonstration than the theory. Practically with- 

 out exception, they agree that the various forms of life 

 have developed from common ancestors through an 

 evolutionary process. When it comes to explaining 

 how this happened, there is plenty of room for differ- 

 ences of opinion, owing to the complexity of the subject. 

 There is no single cause, no simple explanation ; and 

 like the blind men of India who examined an elephant, 

 scientific workers have magnified the importance of 

 .their particular points of contact. For example, it 

 appears to be very difficult for the experimentalist to 

 conceive of processes which cannot be demonstrated in 

 the laboratory, changes requiring thousands of years. 

 On the other hand, it is hard for the philosophical 

 biologist, who sees things in the large, to realize the 

 importance of little things. He will, as it were, draw 

 large checks on the bank of Nature, not realizing that 

 there may be obstacles to getting them cashed. This 

 error was the prevailing one some years ago, but today 

 the tendency is too much in the other direction. In our 

 very proper zeal for tangible facts, we have lost some of 

 the breadth of view and power of imagination which are 

 necessary for scientific progress. 



2. Since we agree as to the fact of evolution, we can Uniformity 



all join in our search for the evidences of its occurrence, oftheessen- 



tial laws of 



First of all, we note the extraordinary uniformity which life 

 underlies all the manifestations of life, animal or vege- 

 table. Protoplasm is everywhere the living substance, 



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